This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The goal is to characterize a unique ganglion cell population that contains a novel photopigment and is intrinsically photosensitive;these ganglion cells play a key role in entraining human circadian rhythms, driving the pupillary light reflex and may also participate in color perception. This project marks the first steps in the analysis of novel visual pathway and photopigment, not previously recognized in the primate visual system. We have started a collaborative project with King-Wai Yau, employing a human antibody to the putative photopigment melanopsin, and have now determined the detailed morphology and spatial distribution of these ganglion cells in both macaque and human retina. Using retrograde photodynamics we have begun to define the central targets of these cells, showing that these cells project widely to both the superior colliculus and lateral geniculate nucleus as well as the pretectal olivary nucleus. We have targeted these cells in vitro for detailed physiological analysis and have characterized cone inputs, rod inputs and the spectral tuning and dynamics of the intrinsic light response. Intracellular recordings show that both the intrinsic and cone-mediated signals converge to confer unique luminance coding and chromatic properties to this ganglion cell.